As is well known in the power generation industry, coal typically used to generate electricity is dried, pulverized into a fine powder and fed into a boiler to be burned. The resulting combustion is used to generate heat, then steam and electricity.
A pulverizer is typically used to crush and dry the coal. Coal is fed into the center of a rotating table. Three metal rollers, herein referred to as tires, push down on the table and exert many tons of pressure onto the table. As the table rotates, the coal moves outward and under the tires where it is pulverized. During this pulverizing process, hot air is blown through the milling area of the pulverizer to dry and transport resulting coal dust out of the pulverizer. At the top of the pulverizer, a mechanical classification takes place where any uncrushed coal is sent back to the center of the table and crushed again. Any fine grained coal is blown out of the pulverizer.
During the pulverizing process, current (amps) on the table motor is monitored. A differential gas pressure (typically air plus coal dust) across the milling area of the pulverizer is also monitored. These measurements are used to approximate physical characteristics of the pulverizer. However, a method or system for measuring the coal bed height inside the milling area is needed.
It is desirable to accurately measure a level of the coal bed in an online coal pulverizer. One problem associated with such a task is in part because of the harsh environment that exists where the coal is being pulverized. By way of example, it is desirable to measure the height of the coal bed inside the coal pulverizer. However, temperatures inside the pulverizer when it is running typically range between 150-400 degrees Fahrenheit. Further, pulverized abrasive coal is constantly being blown around inside the pulverizer in a turbulent fashion. It is therefore difficult to provide typical measurement instrumentation, especially typical precision instrumentation that can operate for long periods of time in such a hostile environment.